Metal zip ties. I used these:
TEVADO 100PCS Metal Cable Zip Ties Heavy Duty 11.8 Inch, Premium Stainless Steel Zip Ties Exhaust Wrap with 198LBS Tensile Strength, Multi-Purpose Self-Locking Metal Wrap Ties for Indoor and Outdoor https://a.co/d/ePIaV8z
Get her to a vet, asap. I've had some chickens behave the same way. Stand-offish, not moving much, if at all. Turned out to be Egg yolk peritonitis; deadly. Good luck!
Looks great! Just make sure there aren't any drafts in there. Ventilation is good but drafts are bad.
https://www.fresheggsdaily.blog/2018/10/chicken-coops-101-drafts-vs-ventilation.html